Subject-Specific Studies of CSF Bulk Flow Patterns in the Spinal Canal: Implications for the Dispersion of Solute Particles in Intrathecal Drug Delivery

Abstract

BACKGROUND AND PURPOSE: Recent flow dynamics studies have shown that the eccentricity of the spinal cord affects the magnitude and characteristics of the slow bulk motion of CSF in the spinal subarachnoid space, which is an important variable in solute transport along the spinal canal. The goal of this study was to investigate how anatomic differences among subjects affect this bulk flow. MATERIALS AND METHODS: T2-weighted spinal images were obtained in 4 subjects and repeated in 1 subject after repositioning. CSF velocity was calculated from phase-contrast MR images for 7 equally spaced levels along the length of the spine. This information was input into a 2-timescale asymptotic analysis of the Navier-Stokes and concentration equations to calculate the short-and long-term CSF flow in the spinal subarachnoid space. Bulk flow streamlines were shown for each subject and position and inspected for differences in patterns. RESULTS: The 4 subjects had variable degrees of lordosis and kyphosis. Repositioning in 1 subject changed the degree of cervical lordosis and thoracic kyphosis. The streamlines of bulk flow show the existence of distinct regions where the fluid particles flow in circular patterns. The location and interconnectivity of these recirculating regions varied among individuals and different positions. CONCLUSIONS: Lordosis, kyphosis, and spinal cord eccentricity in the healthy human spine result in subject-specific patterns of bulk flow recirculating regions. The extent of the interconnectivity of the streamlines among these recirculating regions is fundamental in determining the long-term transport of solute particles along the spinal canal.

Assessing Cerebrospinal Fluid Flow Dynamics in Pediatric Patients with Central Nervous System Tumors Treated with Intraventricular Radioimmunotherapy

“…Several pathologic states are known to disrupt CSF flow dynamics, including the presence of bulk leptomeningeal deposits, postsurgical adhesions, and Chiari malformations (4). Recently, MRI studies have shown that anatomic differences, including lordosis and kyphosis, among healthy subjects affect CSF bulk flow; spinal cord eccentricity in the healthy human spine results in subject-specific patterns of recirculation of bulk CSF flow in certain regions (5).…”

A one-dimensional model for the pulsating flow of cerebrospinal fluid in the spinal canal

“…For a given subject, the necessary anatomical data can be determined from high-resolution MRI images, as explained for instance in Coenen et al. (2019). The computations reported below correspond to two subjects: a healthy 27-year-old female with cm, mm and (subject 1); and a healthy 39-year-old male with cm, mm and (subject 2), both with cardiac period s. The functions and shown in figure 1( b ) are obtained by the boundaries of the binary image stack resulting from segmentation of the high resolution MRI images.…”

“…The results are compared in figures 2 and 3 with flow rate measurements acquired at 12 vertebral levels using PC-MRI with retrospective cardiac gating in in vivo experiments involving the two subjects (see Coenen et al. (2019) for details of the data-acquisition process). To establish a quantitatively consistent comparison, the results are presented in normalized form.…”

“…The solution depends on the anatomical characteristics of the SSAS, including its length L, average cross-sectional area A o and geometric functions  = A/A o and ˆ = /A 1/2 o . For a given subject, the necessary anatomical data can be determined from high-resolution MRI images, as explained for instance in Coenen et al (2019). The computations reported below correspond to two subjects: a healthy 27-year-old female with L = 60 cm, A o = 182 mm 2 and α = (A o ω/ν) 1/2 = 40 (subject 1); and a healthy 39-year-old male with L = 64 cm, A o = 138 mm 2 and α = 35 (subject 2), both with cardiac period T = 2π/ω = 1 s. The functions Â(ξ ) and ˆ (ξ ) shown in figure 1(b) are obtained by the boundaries of the binary image stack resulting from segmentation of the high resolution MRI images.…”

“…The computation of Q involves 10 Fourier coefficients B n , corresponding to the function Π(τ ) shown in figure 1(b), taken as representative of a healthy state ICP waveform (Di Ieva, Schmitz & Cusimano 2013). The results are compared in figures 2 and 3 with flow rate measurements acquired at 12 vertebral levels using PC-MRI with retrospective cardiac gating in in vivo experiments involving the two subjects (see Coenen et al (2019) for details of the data-acquisition process). To establish a quantitatively consistent comparison, the results are presented in normalized form.…”